The night sky as it should be seen – a time-lapse video of the sky above the Anglo-Australian Telescope at Siding Spring

November 16, 2011

By Nick Lomb

Time-lapse video of the sky above the Anglo-Australian Telescope at Siding Spring filmed by Ángel Rafael López-Sánchez. Courtesy Australian Astronomical Observatory, Department of Innovation, Industry, Science and Research

The Anglo-Australian Telescope is located at Siding Spring near Coonabarabran in NSW. The site is a good dark site far away from cities that pollute the night sky with their excess light thrown into the sky. It houses most of Australia’s main optical telescopes including the UK Schmidt Telescope that is also part of the AAO and the ANU’s 2.3-metre telescope and its new SkyMapper telescope.

Ángel Rafael López-Sánchez is a Spanish astrophysicist who holds a joint appointment with the AAO and Macquarie University in Sydney. He took the video over a period from June to September 2011. Preparing the video was not easy as each of the 3800 frames that make up the video represents 12 minutes of exposure time and each frame had to be processed manually. Then there a variety of hazards Ángel had to confront including poor weather and obstruction by kangaroos.

In the video we can see many features in the sky that we city dwellers miss out on. First there is the sheer overwhelming number of stars – in a previous post we estimated the number of stars visible at anyone time to the unaided eye from a dark site as 2400. This is in contrast to the view from the centre of a major city like Sydney or Melbourne where only about 125 can be seen on a good night.

There is one, and only advantage, of seeing the sky from a light-polluted area, which is that from there it is easier to become familiar with the bright stars and constellations in the sky. I always suggest to people going for country holidays to use the Australian Sky Guide to become familiar with the night sky just before they leave for their holiday so that they can orient themselves when they see the spectacle of the real sky.

For much of the video the white band of the Milky Way, made up of innumerable faint stars, is prominent. It is criss-crossed by dark regions that are due to clouds of dust blocking the light from the stars behind. At one stage the video shows the steady westward movement of the Southern Cross. From a city we recognise the Cross thanks to the two Pointer stars that always accompany and point to Australia’s favourite constellation. In the video, as from a dark sky, the Cross can be identified by the dark cloud, the Coal Sack nebula, that lies near its two brightest stars, Alpha and Beta Crucis. The Coal Sack is the head of the famous Aboriginal dark constellation of the Emu.

As dawn breaks near the end of the video, we can see the two Magellanic clouds, the nearest companions to the Milky Way galaxy, still patiently circling the South Celestial Pole. After viewing this spectacular video, I feel nostalgic for a glimpse of a real dark sky. I will need to organise a trip away soon!

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